Various federal and state agencies in the United States, as well as European and other national regulating agencies have announced or established regulations requiring a reduction in the volatile organic chemicals (VOCs) released from surface coatings, or paints. In general, solvent-based surface coatings are eventually prepared for use by the addition of one or more pigment dispersions containing pigments and other additives in order to achieve the colors, hues and tints desired by the user. In some cases, the pigment dispersions, are added at the paint manufacturer's facility to a clear base or to an opaque base that contains titanium dioxide or some other white pigment to produce the finished paint, or a tinted precursor base. In many other instances, custom tinting occurs at the point of sale (POS), or at a depot, or in-plant at the paint manufacturing facility by addition of one or more pigment dispersions to a clear base or to an opaque base containing a white pigment.
Regulations concerning VOC content vary depending on the region or state in the US or the international jurisdictions. The most stringent limits were originally developed in California for architectural and industrial maintenance (AIM) coatings. In Europe, in an effort to combat ground level air pollution, the European Union Directive 2004/42/EC was promulgated to minimize, monitor and control the effects of VOCs.
Currently, in some jurisdictions, the VOC content of pigment dispersions is not included in the VOC calculation for point of sale, although it must be included for in-plant tinting of the base or finished paint. However, proposed changes in legislation would include the VOC contribution of the pigment dispersion that is added at the POS as well as depot tinting. Therefore, the selection of raw materials is an important criteria to the paint formulator in terms of the VOC contribution of the pigment dispersions to the finished coating or paint.
In order to minimize the VOC content of the finished tinted surface coating or paint, consideration must be given to any VOC that is contained in the pigment dispersion used to tint the paint base to produce the finished paint.
Solventborne colorants, or pigment dispersions, for tinting solvent-based coatings can have a VOC content that ranges from 300 g/L and higher. Historically, these VOC values have been commercially acceptable to manufacturers of finished paints into which the pigment dispersions were incorporated at the manufacturer's facility, or to manufacturers that marketed paint bases for custom tinting at the point of sale, e.g., at retail paint stores and the paint department of home center stores. However, as environmental awareness and concerns of consumers have grown, and governmental agencies have imposed stricter regulations regarding the release into the atmosphere of VOCs, the paint industry has sought means for reducing the VOC content of its products. It would therefore be desirable to provide pigment dispersion and systems containing a number of pigment dispersions of different colors that have a low or reduced VOC content for use by paint manufacturers in their own facilities, at third party tinting facilities, and for the retailers that provide custom tinting services at the point of sale, which would thereby reduce the overall VOC content of the finished paints containing the pigment dispersions.
The present invention is directed to the problem of a formulating solventborne pigment dispersion compositions having a reduced VOC content as compared to prior art pigment dispersions and providing pigment dispersions which can be used to tint solventborne paint bases having a variety of different chemistries.
The invention also addresses the problem of formulating a solventborne pigment dispersion of relatively low VOC content that has minimal adverse effects on the desirable physical properties of the paint bases to which it is added, including the finished paint's rheological properties and the properties of the cured paint film.
A further problem addressed by the present invention is providing a pigment dispersion that can be used to tint-solvent-based surface coatings to provide a finished surface coating that will have a reduced VOC content in relation to comparable available products in order to assist paint manufacturers and marketers to meet the increasingly strict regulations regarding VOC emissions into the atmosphere.
More specifically, a goal of the present invention is to provide solventborne pigment dispersion compositions having no more, and preferably less than 250 g/L of VOC.